Heat treated rail and method of heat treating the same



April 6, 1937. 5 GEORGE 2,075,842

HEAT TREATED RAIL AND METHOD OF HEAT TREATING THE SAME Filed Sept. 6, 1933 INVENTOR HARRY 5 aka/m5 Patented Apr. 6, 1937 PATENT OFFICE HEAT TREATED RAIL AND METHOD OF HEAT TREATING THE SAME Harry S. George, Massapequa, N. Y., assignor, by

mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York Application September 6, 1933, Serial No. 688,334

Claims.

This invention relates to heat treated rails and to a method of heat treating them.

In recent years considerable study has been given to the problem of increasing the lifeof 5 rails by eliminating rail batter, and this problem is not only confined to tracks but it has also assumed importance in switch-points, frogs, and. crossings. The tread surfaces at the ends of rails at joints in track become battered to a lower level than other portions of the tread surfaces of rails, because at the ends of rails there is no support against end flow of rail metal at the tread surfaces thereof; hence, the rate at which tread surfaces of rails become battered is greatest at rail ends. This lowering of the running or tread surfaces of rails at rail'joints increases the effect of the pressure of rolling v trafiic by converting it into a downward blow as the wheels pass over rail joints. This action still further increases the rate at which the tread surfaces at the ends of rails become battered over that of the rest of the rails. After a few years of service the amount of batter at rail joints becomes so great that it is necessary to build up the tread surfaces at the ends of rails to the general level of the rails bydepositing metal on the depressed areas.

In order to prolong the life of new and substantially unworn rails, it has generally been the practice to harden the tread surfaces at the ends of rails by heat treatment, so as-to retard the rate of batter. Heretofore, the only methods of heat treatment which have proved practicable employ an external quenching medium, such as water or an air blast. In most cases the treatment has included a tempering operation. Although it is possible to attain the desired results with such methods when great care is employed, the methods are very difficult because of the sharp corners at the tread surfaces at the ends of rails. Certain precautionary measures are necessary if any success is to be attained in safe guarding against cracks or the setting up of internal stresses in the tread surfaces which, when combined with repeated stresses from service, often result in the eventual cracking of the corners of rail ends. These precautionary measures include the very gradual application of heat, especially at 'the corners of the tread surfaces at rail ends. This is especially true when a secondary tempering operation is employed, because of the extra hazard entailedin the drastic application of heat to steel in ahardened state. Heretofore, these precautions have not been taken into consideration in heat ing a rectangular area.

treating rail ends in tracks, perhaps from ignorance or for economic reasons or the practical difficulties encountered. As a consequence of the cracking tendency of the tread surfaces at rail ends and for other reasons, the hardening of rail 5 ends has not generally proved very successful. None of the former methods have employed precautionary measures for avoiding the direct application of heat to the extreme end edges of rails, so as to insure an entire area heat treated 10 of reaching a uniform elevated hardening temperature.

It has also generally been the practice to harden the tread surfaces at rail ends by heat- This practice is objec- 15 tionable, because of the abrupt transition between the hardened heat treated tread surface area and unhardened tread surface area adjacent. thereto.

In order to facilitate an understanding of this 20 invention in which an improvedand eflicient meth-' od is employed for heat treating the tread surfaces at the ends of rails, it seems expedient at the outset to consider the manner in which rolling trafiic tends to cause deformation of the tread 25 surfaces of rails. As the wheels of rolling stock move over a track, the tires of the wheels bear on astrip of tread extending from about the middle of the rail head toward the outside edge thereof but not reaching the outside edge. After 30 months of service this strip tends to broaden toward the inside edge of the rail head, finally reaching it as the rail tread surface wears down and the contour of the rail takes on the shape of the tire. This is particularly true where rails 35 are substantially vertical or canted not more than 1 in 40. The above is also true to a lesser extent where rails are canted as much at 1 in 20, but in such cases a longer time is required for the tires of wheels to bear on the inside edges r the rails are substantially vertical or only slight- 50 ly canted, the width of a heat treated tread surface area is preferably decreased gradually toward a point back of the rail end, and from the outside to the inside edge of the rail head,

so that the transition zone between the treated 55 and untreated tread surface areas extends approximately diagonally across the rail head. In cases where rails are canted a considerable amount and where track maintenance is such that the greatest wear occurs from the middle to the outside edges of rail heads, the width of a heat treated tread surface area is preferably decreased gradually to a point back from the rail end, and from the inside to the outside edge 01 the rail head.

Therefore, at no point in its travel will a wheel abruptly pass from a hardened to an unhardened part of a rail tread surface or vice versa. Moreover, by terminating the heated area diagonally across the rail head, the heat treated area is of such shape that it is utilized most effectively. For example, where rails are not canted or only slightly canted, the greatest wear occurs at the inside edges of the rail heads. In such cases the inner edge of a rail head is heat treated a greater distance back from the end of the rail than the outer edge, where the least wear occurs.

An important object of my invention, therefore, is to heat treat tread surface areas at the ends of rails so that the length of a heat treated area longitudinally of a rail is-longest at the edge of the rail head where the tendency of the rail metal to wear and flow is greatest.

Another object of my invention is to heat treat tread surface areas at the ends of rails in such a manner that rolling traffic will not pass abruptly from a hardened to an unhardened portion of a tread surface area or vice versa. A further object of my invention is to provide an improved method of hardening tread surface areas at the ends of rails with a single application of heat, and without the necessity of using any external quenching medium.

A further object of my invention is to provide an improved method of uniformly hardening tread surface areas at the ends of rails by applying heat indirectly to the extreme end edges and corners of the tread surfaces of rails, so as to attain an approximately uniform hardening temperature over an entire heat treated tread surface area.

A further object of my invention is to provide an improved method of heat treating tread surface areas at the ends of rails in which a high temperature heat having a substantially constant rate of heat output is applied to the areas for a predetermined length of time.

The above and further objects of my invention will become apparent in the following description and drawing, in which:

Fig. 1 shows the end of a rail with a fragmentary view of a wheel of rolling stock bearing thereon;

Fig. 2 is a perspective view of the end of the rail shown in Fig. 1, after being subjected to Wear;

' Fig. 3 is a sectional view taken on line 3'-3 of Fig. 2; and

Fig. 4 is a perspective view of abutting rail ends at a rail joint and a blowpipe disposed over the same for manually heat treating the tread surfaces of rails in accordance with the principles of this invention.

The various figures of the drawing illustrate rails which are substantially vertical and not canted. The manner in which trafiic tends to cause deformation or wear at the ends of such rails in a straight track will now be considered, in order to illustrate one manner of heat treating rail ends in accordance with the principles of my invention.

Referring to Fig. 1 of the drawing, I have shown the tire 4 of a wheel 5 of rolling stock bearing on the running or tread surface 6 of a rail 1 comprising a head 8, web 9 and flange H]. In this instance it will be noticed that the tire 4 bears approximately on the middle portion of the tread surface 6 and inside edge ll of the rail head 8, but does not bear on the outside portion of the tread surface 6 or outer edge l2 of the rail head 8. After the rail has been subjected to service, the tread surface metal begins to flow, and this fiow is more pronounced at the extreme end of the tread surface. After considerable wearing and flowing of the rail metal at its tread surface, the tire 4 bears against a worn tread surface indicated by the dotted line 6 in Fig. l. Afte' months of service, the battered worn area l3 in Fig. 2 is produced, which slopes downward toward the extreme end edge I4 and inner edge ll of the rail head 8, and the rail metal flows over the end edge [4 of the rail head, as indicated at l5 in Fig. 2. Thus, the greatest wearing of metal on the tread surface at the end of new rail in a straight .track, which is substantially vertical or only slightly canted, occurs at the extreme end edge M of the rail head, and the inside and middle portions of the tread surface 6 of the rail head. As the end edge l4 wears down, the tire 4 bears farther across the tread surface 6 until finally the outer edge l2 also wears near the end edge l4.

' With the above considerations in mind, as well as the objections of an abrupt transition zone between hardened and unhardened tread surface areas, which result when rectangular heat treated areas are produced at the tread surfaces at the ends of rails, I preferably heat treat the tread surfaces of rail ends so that the boundary between the heat treated areas IB and untreated areas l6 adjacent thereto extends approximately diagonally across the rail, as indicated by the dotted lines I! and H in the rail joint shown in Fig. 4. It can thus be seen that, by varying the widths of heat treated tread surface areas where they terminate back from the extreme ends of rails, the transition zone between the hardened and unhardened areas l6 and I6 will extend over a considerable distance of the heads 8' of tl:e abutting rails l in a longitudinal direction. When traific approaches the rail joint in the direction indicated by the arrow, the weight of the trafiic is borne by both a heat treated tread surface area IG and untreated area I6 at the same time. In this manner the rolling traffic will not pass abruptly from a heat treated area to an un treated area or vice versa.

By forming the heat treated areas H3 in the present instance with the inside edges ll of the rail heads 8' heat treated a greater distance back from the extreme end of the rail than the outside edges l2' of the rail heads, the distribution of hardening is utilized most'eifectively; that is, the portions of the tread surface of the rail end which will be subjected to the greatest amount of wear receive the most heat treatment. By hardening small tread surface areas of approximately trapezoidal shape at the ends of new or substan tially unworn rails, as described above, a considerably larger worn area is avoided, thereby prolonging the life of. the rail. For example, if the end of the rail 7 in Fig. 2 had been heat treated 70 When heat treating with It, the much larger worn area l3 would have been avoided.

, It is desirable, at least for economic reasons, to heat treat a minimum area of the tread sur- 5 faces at the ends of rails. I have found that a substantially trapezoidal or similar-shaped heat treated area, as illustrated in Fig. 4, is particularly desirable, because for a given and sufficient depth of heat treatment in the tread surface of ill a rail, it is the smallest area which will also give sufficient length longitudinally of the rail in such a manner that the area is effectively utilized to prevent wearing and flowing of the rail metal.

Although heat treated rail ends may be produced in many different ways, the trapezoidalshaped heat treated area particularly lends itself to 'my preferred method in which a heat treated area is allowed to cool naturally without employing any external quenching-medium, such as an air blast or water. It is to be understood that the expression natural cooling signifies the combined cooling effect of v convection and radia- 'tion of heat from the rail to the surrounding air plus the cooling effect of the underlying and adjacent mass of rail which is relatively cool. I have found that the latter effect is much greater than the cooling effect of air where a relatively small tread surface area of an ordinary railis heated.

In order to produce a substantially uniform and satisfactory condition of hardness of tread surface areas with natural cooling, it is desirable to control both the temperature to which a tread surface area is heated and the depth of penetration of the heat. This can be accomplished by employing a high temperature heat having a substantially constant rate of heat output, and applying such heat to tread surface areas for a predetermined length of time. This insures the 40 heating of tread surface areas to an elevated temperature, before too much heat has penetrated into the mass of the rail, and also avoids the use of a source of heat of such intensity that only a superficial or skin hardening is effected. The elevated temperature to which the tread surface areas are heated is such that, when the heat treated tread surface metal is allowed to cool, it will harden; and throughout the specification and claims this elevated temperature is termed an elevated hardening temperature.

Iprefer to use a high temperature gas flame or flames as the source of heat, and for this purpose employ a suitable burner, such as a blowpipe l9.

The blowpipe is supplied with a combustible gas, such as a mixture of oxygen and acetylene, from a suitable source of supply (not shown), at a flxed pressure. After the heathas been applied to a tread surface areafor a predetermined length of time, the application of heat is stopped. The

0 underlying mass of the rail will remain relatively cool and exert a quenching effect on the heated tread surface. area by withdrawing heat therefrom to cool and uniformly harden it naturally. By standardizing on a certain size flame and timing the application of the flame on a tread surface area, a simple method of controlling the heat treating of tread surfaces at rail ends is obtained to produce uniformity of-hardness and depth of I heat treating.

an oxy-acetylene flame, a strictly neutral flame can be used. Since frequent adjustments may be necessary to maintain a strictly neutral flame, an excess acetylene flame having a "feather" of excess acetylene of 75 about we to 2 times the length of the inner cone is preferred, because of the additional benefits obtained, such, for example, as the protection of rail metal from oxidation.

The trapezoidal-shaped heat treated tread surplied that the trapezoidal-shaped areas 16 are heated uniformly to an elevated hardening tem- 3 perature of about 1600", F. When the heat has penetrated into the tread surface of the rails I to a considerable depth, such as inch, for example, the application of heat is stopped. For a.

given size rail and size of area to be heat treated,

the length of time of applying heat to obtain the required depth of heat treating can readily be determined by trial. After the time is once fixed,

the tread surfaces of rails in a section of track can be heat treated uniformly. In order to avoid overheating the corners of the tread surfaces at the ends of rails, the source of heat is not directly applied on the extreme end edges and corners of the rail tread surfaces. The conduction of heat to the corners of rails from the heated portions adjacent thereto is suflicient to raise the corners to the same elevated hardening temperature as the remainder of the heat treated areas.

From an observation of the performance of rails of standard composition under modern traffic conditions, I have discovered that heat treated tread surface areas at the extreme ends of rails at joints should possess a hardness of at least Scleroscope after being subjected to service, if they are to withstand the tendency to flow. In order to attain this hardness, the heat treated tread surface areas at the ends of rails must have a Scleroscope hardness of about 50 to- 52 after heat treatment and before they are sub-' jected to service. Scleroscope hardness increases to about 60 after being subjected to service or cold work, as it is commonly called. Thus, the hardening due to cold work further tends to prevent deformation and wear of the tread surface areas at the ends of rails, and therefore constitutes a beneficial or protective action. The Scleroscope hardness of,

about 50 to 52 corresponds'to a Brinell hardness of about 350, and it has been found that the increase in hardness due to cold work, being very shallow, is not generally indicated by the Brinell test, so that it remains substantially unchanged.

Ordinary rails usually contain from approximately .55 to .80 per cent carbon and a similar amount of manganese, and it has been found that they readily respond to heat treatment when allowed to cool naturally from an elevated hardening temperature. By way of example, with the method of heat treating described above, it has been possible to obtain a hardness as high as It'has been found that this 420 Brinell. The corresponding Scleroscope ods, as it is not necessary to provide and move equipment for quenching the heated-tread surface areas with an external quenching medium,

such as water or an air blast.

It will thus be seen that an improved and simplified method of heat treating tread surfaces of rails has been provided. By making the hardened areas at the ends of rails of approximately trapezoidal shape, there is the further economy in the amount of heat required, as compared with producing hardened areas of rectangular shape, 10 to obtain the same effective length of hardening along rails.

While I have shown and described one particular manner of applying heat and of cooling to provide trapezoidal-shaped hardened areas at the ends of rails, it will be obvious that such areas may be obtained in other ways and with other sources of high temperature heat. Another method of producing a similarly shaped area harder than the adjoining tread surface of 20 the rail is disclosed in copending application Serial No. 688,333, filed September 6, 1933. I desire it to be understood, therefore, that my invention is not to be limited to the particular embodiment disclosed, nor to the particular shape 2 of heat treated areas illustrated, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

I claim:

30 1. A rail having at an end thereof tread surface area hardened by heat treatment, said area being of such shape that at least a sufficient portion of the boundary back from the end of the rail between said area and the untreated 35 portion of the rail tread surface adjacent thereto extends approximately diagonally across the rail tread surface to provide a run-off which will prevent rolling stock from passing abruptly from a hardened tread surface area to an untreated area or vice versa.-

2. A rail having at an end thereof tread surface area hardened by heat treatment which is of such shape that one edge of the rail head is heat treated a greater distance back from the end of, the rail than the other edge thereof to provide a run-off which will prevent rolling stock from passing abruptly from a hardened tread surface area to an untreated area or vice versa.

3. A rail having at an end thereof tread surface area hardened by heat treatment which is of such shape thatpne inner edge of the rail head is heat treated a greater distance back from the end of the rail than the outer edge of the rail head to provide a run-off which will prevent rolling stock from passing abruptly from a hardened tread surface area toan untreated area or vice versa. I

4. A rail having adjacent an end thereof a tread surface portion comprising metal having a greater hardness than the adjoining rail metal, said harder portion being of such shape that at least a suflicient portion of its boundary distant from the end of the rail extends diagonally acrossthe rail tread surface to provide a diagonal run-off which will prevent rolling stock from passing abruptly from said harder portion to the adjoining tread surface.

5. A rail as claimed in claim 4, in which the distance of said boundary from the end of the rail is greatest adjacent the inner edge of said tread surface.

' HARRY S. GEORGE. 

